In doing research I have seen people suggest that lumber from the big box, diy stores IE: Lowes and Home Depot is inferior to lumber sourced from and actual lumber yard. Either way, I have to decide which way I want to put the post in the ground. Concrete is great, until I need to replace the post. And I want it to be easy to replace in case the post gets smashed by the bad drivers. I am inclined just to dig a hole, set the post and tamp the dirt down as I backfill in the hole. In this clay, it will probably set up hard. Decisions, decisions.